Dialysis treatment for patients with renal failure require a ready access to blood vessels in order for blood to be continuously withdrawn from the patient in amounts of over 200 ml/min. The blood withdrawn from the patient is passed through a dialysis machine, and returned to the patient. A very common method of producing this hemoaccess is the use of expanded polytetrafluorethylene (PTFE) tubes as grafts which are surgically placed between an artery and a vein (PTFE AV fistula). This procedure is especially useful in patients who do not have blood vessels which will support the construction of a more traditional primary fistula on the forearm.
These PTFE grafts cannot be used safely to withdraw blood however until they have been in place for a minimum of 14 days after surgery and have become surrounded by fibrotic tissue. Because of the bleeding which occurs at the site of a needle puncture in these grafts if fibrotic tissue is absent, common complications encountered with early puncturing of PTFE AV fistulas are a hematoma surrounding the graft, false aneurysm and possible graft occlusion. The Atlas of Angioaccess Surgery by Pedro A. Rubio and Edward M. Farrell (Year Book Medical Publishers, Inc., 1983), which is incorporated herein by reference, states that "graft fistulas should not be punctured before the third postoperative week. Earlier puncture risks hematoma formation in the subcutaneous tunnel following needle withdrawal, which will result in further delay in healing." Various materials in addition to PTFE have been tried including autologous saphenous vein, Dacron, synthetic polyester fiber velour, modified bovine carotid xenograft, and modified human umbilical vein, but none have overcome the problems associated with early puncture of the graft.
A coaxial double lumen tube for use in hemoaccess wherein the space between the two lumen is filled with a self-sealing, nonbiodegradeable polymer (hereinafter "filled double tubes") has now been discovered. The filled double tube does not bleed upon puncture with a dialysis needle even immediately after surgery. Ex vivo perfusion tests and AV fistula experiments in dogs clearly show that the filled double tubes are superior as grafts to the known single PTFE tube in the amount of bleeding resulting from puncture of the tube with a dialysis needle.
The advantages of the filled double tube are that (1) it can be used for hemoaccess immediately after implantation, (2) the lack of bleeding results in a lower incidence of perigraft hematomas and a lower incidence of pseudoaneurysms, (3) the lack of bleeding upon puncture obviates the need for prolonged compression of the puncture site with secondary occlusion of the tube, and (4) due to the increased rigidity of the filled double tube, puncturing of the tube is easier.